1. Field of the Invention
This invention relates to the field of computer networking, and in particular to a low complexity information exchange management system.
2. Description of the Related Art
Internetworking of high-performance computers has become the focus of much attention in the data communications industry. Performance improvements in processors and peripherals, along with the move to distributed architectures such as client/server, have spawned increasingly data-intensive and high-speed networking applications, such as medical imaging, multimedia, and scientific visualization. However, the interconnections between the systems and their input/output devices cannot keep up with the blinding data rates, nor can they provide the distances needed for local area networks spanning campus-wide areas.
According to "Amdahl's Law", a megabit per second of input/output (I/O) capability is needed for every MIPS of processor performance. Current communications standards top out at just over 100 megabits per second, not nearly fast enough, as technical computing applications already demand processors exceeding 1,000 MIPS. The deficiencies in current transmission rates results in the communications channel becoming a bottleneck to system performance.
A new protocol known as Fibre Channel is 10 to 250 times faster than existing networks, transmitting at rates exceeding 1 Gbps in both directions simultaneously. It defines standard media and signaling conventions for transporting data in a serial fashion, it provides an error correcting channel code and a frame structure for transporting the data, it sets out a flow control methodology, creates some common services, and supports interfaces to existing higher level protocols such as SCSI (small computer system interface). The Fibre Channel protocol can be applied to various network topologies including point-to-point, ring, and switched. The Fibre Channel protocol is being proposed as an ANSI (American National Standards Institute, Inc.) standard, and a multitude of reference material is readily available at http://www.fibrechannel.com.
The higher level protocols supported by Fibre Channel perform "operations" such as: open, read, write, close, etc. Each of these operations corresponds to one or more data exchanges between the local node and a remote node. It is desirable to allow a large number of exchanges to be concurrently active on a given node, since this permits "multitasking" by a node. When a node is waiting on a resource (e.g. waiting for data on a disk to be read into memory) it could simultaneously be fulfilling other requests (e.g. buffering data to be written to disk, sending data already in cache memory to another remote node).
The high data rates require that a large part of the Fibre Channel protocol be handled by hardware. The hardware implementation may incur unwanted cost and complexity, particularly if a large number of concurrent data exchanges are to be supported. Each data exchange must be tracked by the network interface so that the interface can commence, conduct, and conclude each exchange in an orderly fashion, conforming to the specified exchange flow and verifying the validity of each received data frame. The tracking information for each exchange is stored in a corresponding entry in an exchange table. It would be desirable to provide a method for supporting a large number of concurrent data exchanges while maintaining a small exchange table.